1. Field of the invention
The present invention relates to an automatic forging press and, more particularly, to a press for continuously carrying out a plurality of forging processes at a time.
2. Prior art
A generally known automatic forging press comprises a forging device in which a plurality of upper dies are mounted in a row on the bottom side of a slide hanging from an eccentric through a connecting rod so as to freely move up and down, while corresponding lower dies are mounted in a row on the upper side of a bed facing the upper dies, and a transfer device in which materials to be worked are supplied and fed to each die for each step sequentially in order. Finally, press-worked products are taken out from the forging press.
In the press of the above type, a large amount of deformation as well as complicated and accurate configuration never attained by a single forging press can be achieved, because heated materials to be press-worked are supplied from one side, the materials being subject to several processes of plastic deformations by application of pressure, and finally press-worked products are taken out from the other side.
When forging is repeatedly carried out for a long period of time, forging conditions may vary with the lapse of time, and therefore various attempts have been proposed to correct the varied forging conditions thereby securing uniform quality of products at all times.
Prior art disclosed from the foregoing viewpoint can be classified as follows:
1. Art for maintaining a load, applied by dies, constant:
For example, the Japanese Laid-Open Patent Publication (unexamined) No. 61-259900 discloses control of the pressing force applied to materials to be press-worked by arranging an elastic block on the upper side of the upper dies. Other Japanese Laid-Open Patent Publications (unexamined) Nos. 60-102300, 60-12300 also disclose similar presses.
2. Art for maintaining dead point center constant:
For example, the Japanese Laid-Open Utility Model Publication (unexamined) No.60-157097 discloses a press in which the temperature of the die sets 15a, 16a is detected, thereby actuating the slide control motor 43 with the programable controller 44, as shown in FIG. 4 thereof. Other Japanese Laid-Open Patent Publications (unexamined) Nos. 61-169199, 61-169200 and 60-141399 also disclose similar presses.
3. Art for freely performing vertical slide control:
For example, the Japanese Laid-Open Utility Model Publication (examined) discloses a press in which the wrist pin 5b is eccentrically and rotatably mounted on the top end of the connecting rod 3b, and one end of the lever 6b is connected to the wrist pin, while the other end thereof is provided with the adjusting screw 45.
The foregoing prior forging press control means with their respective features are advantageous to overcome the problems pointed out therein.
However, there still remains a problem not solved by the foregoing prior art presses particularly in the automatic press for continuously carrying out a plurality of processes at a time.
In the automatic press of this type, a required press load is separately determined depending on how many dies of all the dies are fed with materials to be press-worked at a certain point of time. For example, a required load when all of the plural dies is fed with the material mounts to five times as large as a required load when only one die is fed with the material.
Usually, automatic forging presses are operated to carry out continous forging press working by establishing their required load on the assumption that each of the plural dies are fully supplied with one material to be press-worked.
Because it is impossible to feed every die for every process with material, intermediate product or finally press-worked product (hereinafter collectively referred to as "workpiece") so long as the time of starting operation and the time of terminating thereof are concerned, a problem exists in that a smaller number of workpieces at those times of starting and/or terminating operation cannot avoid suffering from an excessive load, which results in defective products having such a defect as reduction in thickness or the like. The same kind of problem will arise also during operation caused by overheating of the workpiece itself which brings about failure of the feeding device resulting in interruption of continuous feeding with workpieces.